Periscope and optical system therefor.



G. N. SAEGMULLER & G. A. H. KELLNER.

OPE AND OPTICAL SYSTEM THEREFOR.

PERISC APPLICATION FILED DEC. 6-1915. I 1 370,876. Patented July 2,1918.

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/ ,G'c/Z A TTORNEYS G. N. SAEGMULLER 6L 6. A. H. KELLNER.

PERlSCOPE AND OPTICAL SYSTEM THEREFOR.

APPLICATION FILED DEC. 6. \9l5.

Patented July 2, 1918.

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ASSIGNOBS TO BAUSCH CORPORATION OF NEW YORK.

Specification of Letters Patent.

Patented .J uly 2, 1918.

Application filed December 6, i915. Serial No. canoe.

To; all whom it may concern:

Be it known that we, Gnonon N. SAEGMUL- LER and GUSTAV A. H. KELLNER, citizens of the United States, and residents of Rochester, in the county of Monroe, State of New York, have invented certain new and useful Improvements in Periscopes and Optical Systems Therefor; and we do declare the following to be a full, clear, and exact description of the same, reference being had to the accompanying drawings, forming a part of thisspecification, and to the figures and letters of reference marked thereon.

Our invention relates to optical instruments that are adapted to receive light pencils from any one of a plurality ofeneral directions and direct such pencils a ong a certain predetermined course. More par ticularly our invention relatesto telescopes such as are knownas periscopes.

Heretofore in the use of the eriscope in submarine and in other places w ere the observer is confined and dependent upon the periscope for his outlook, his vision has. been restricted to a zone extending in a substantially horizontal direction from the u per prismof the periscope, atwa comparatively narrow angle, and any object overhead for a considerable distance has been entirely out of the observers view. For this reason submarines are liable to be taken unawares by aeroplanes and thus become unduly exposed to attack from that quarter.

An object of our present invention is to enable an observer within a submarine to be able to see the entire horizon, including the sky above him, even though the submarine be submerged. Another object is to provide an optical instrument having the general form of a periscope, and adapted to viewing in either of two general directions, disposed" at an angle to one another, the possible field of view of such an instrument comprising the sum of the angles of view in both directions, which may cover substantially a hemisphere. Another object resides in providing means whereby these ends are readily accomplished. Another object is to provi e means that may be incorporated in dioptric or telescopic instruments whereby said instruments may be used to view objects in any one of a lurality of directions at will. Another ob ect is to provide an optical instrument so organized that an observer pointed out in partlyin section,

may alternately or successively view objects lying in a plurality of directions. Still another object is to provide an instrument adapted to viewing objects in a plurality of directions without necessitatin the moving of the instrument bodily. ther objects will hereinafter become apparent.

To these and other ends our invention consists in certain improvements and combinations of parts all of which will hereinafter be described, the novel features being the claims at the end of the specification.

Figure 1 is an elevation of a periscope embodying features of our invention, certain parts of the instrument being shown in posltion for lateral or horizontal sighting.

Fig. 2 is a vertical longitudinal section on ,an enlarged scale, of the head or upper rtionof the instrument shown in Fig. 1, ooking to the left of the instrument as shown therein; certain parts of the instru ment in this figure being shown in position for longitudinal or aerial sighting.

Fig.3 is a vertical section on an enlarged scale of a form of head qualified to be embodied in a periscope to the exclusion of the formshown inFig. 1. I

Figs. 4 and 5 are fragmentary portions of *Fig.v 3, showing certain elements of the structure in different positions.

Fig. 6 shows an optical system for our improved instruments.

Fig. 7 shows the optical system shown in Fig. 6 with certain elements of the system in different positions.

Fig. 8 shows another optical system.

Like characters of'reference throughout the several figures indicate the same parts.

Referring now more particularly to the structure and apparatus illustrated: the numeral 1 indicates the periscope head as a unit. 2 indicates the periscope tube or casing which passes through portions of a submarines structure as shown in Fig. 1, and indicated by 3 and 4. The periscope is supported usually in a vertical position by means of the thrust bearing 5 which rests on the bracket 6. 7 denotes the lower end or' ocular unit of the periscope. A hand wheel 8 is provided, which. by means of its shaft 8 and a pinion (not shown) cooperates with the internal gear portion 6 of the bracket the entire periscope windows, a vertically disposed or lateral window and a horizontally disposed or axis of the periscope, in a cell 10 periscope and is overhead window 11. The lateral window 10 is mounted with its axis intersecting the which is threaded into a suitable aperture in the side of the periscope head. The window 11 is mounted'coaxial with the axis of the periscope, in a cell which forms a cap 11*, threaded into the top of the head 1. Within the cap or cell 11 is mounted a negative lens combination 12, by means of a cell 14 which also serves to hold the window 11 in place. 1 Within the head 1, and in the vicinity of the intersection of the axes of the windows 10 and 11, is mounted a slidable carriage 20, operating within a tubular sleeve or guideway 21, .said carriage and sleeve being provided respectively, with a spline and splineway 22 ad apted to constrain the carriage against rotative movement about its longitudinal axis. A rack 30.-.is-

secured along one side of the carriage as shown, said rack being engaged by pinion 31, mounted at the upperend of shaft 32, which shaft is ofiset by means of universal joints 33, whereby to permit the use of-as large aperture lenses as are needed in the' intermediate portion of the periscope system.

The lower end of the shaft 32 is connected by means of a flexible coupling '34 which in this case, is an .Qldham 'cou'pling,- to the bevel gear 35 which meshes with bevel gear 36, both gears-bein journaled in the bracket 37. The end of t e' gear 36 protrudes whereby the sha t 32 may be rotated- 1n either direction and thereby elfect the axial movement of the carriage 20 through the agency of the pinion 31 and the rack 30.

y prising a field or '65 The objective40 secured in the mount 41 is mounted preferably in close proximity to sleeve 21 and coaxial with theaxisofthe periscope, the diaphragm 42 is mounted in the focal plane of objective 40, and a col lective lens 43 is mounted preferably as shown in the lower portion of the head 1.

In the ocular unit 7 in proximity to the ocular member proper 7 and at the-intersection of'the longitudinalaxis of the periscope and the axis of the ocular, is mounted preferably a roof prism 50. Within the ocular member 7 a and in the focal plane F (see Fig. 1) is mounted a reticule 51, provided with cross hairs, and an ocular comc'ollecting lens 52, and an eye lens 53 is provided. The ocular is movable relatively to the reticule 51, whereby the instrument may be accommodated to eyes of different observers.

The lens system intermediate the collective lens 43 and the prism is shown in Figs. 6 and 7 and will hereinafter be described.

The sleeve, 21 wherein the, carriage 2O slides, is provided with alined apertures 21- and 21", disposed in the axis of the periscope, and registering respectively withthe negative lens combination 12 and the 0bjective 40. The sleeve is also provided with an aperture 21 registering with window 10.

The carriage 20 consists of a tubular por-.

tion open at one end and terminatin at the other end in a wall or partition '20. ithin the carriage 20 is mounted, a penta prism which is secured to the wall 20 by means of studs 61 and a strap. 62, see Figs. 1 and 2. Suitable cleats 63 are provided on the wall -20 to accurately locate and hold the prism 60 in place. sitioned that when the carriage 20 IS in the extreme left hand position of movement, viewing the instrument as shown in Fig. 2,

the prism registers simultaneously with the lens combination and the objective respecvtively. In order to keep the carriage 20-111v "shaft 38 of thebeveL" through the wall. of the. rovided with a knob .might be caused the position to which the carriage has been moved by the rack"-and pinion movement, and .to prevent the carriage sweeping back "andforth in its sleeve-20 accidentall as w e by therolling or pitc ing of the ship in which the instrument ismount The prism 601s so po- 5 'Suitable apertures 72 and 73 are provided. to register with the negative ed, are provided notches 80 and 81, and a sprilpg pawl 01' detent 8'2 cooperating therew1t Thus, with the mechanism, thus far: described, the observer placing his eye at 53 and adjusting the ocular thereto may, 'by manipulating-the knob 39, to the right or to the left, be able .to see laterally, lthrough window 1O when the elements of thejnstru- I ment are, intheposition shown in .1, or view objects overhead or'inthe sky, t ougl} -window 11, when the elements of the instrument are in the position shown in Fig. 2,xtraneous light from the Window not in use being screened off by;\ the wall of the carriage which covers t e aperture not in use in a manner similar to a three-way valve.

In Fig. 3 is shown a form of head where in the elements of theinstrument that are to be changed and substituted are carried in a revolving turret or drum. This instru ment incorporates in addition to the system described in the apparatus disclosed in Fig. 2 an additional system for lateral sighting. In this structure the head as a unit. Within the head is mounted a revolving turret or drum, which carries the elements of the structure and system to be substituted or changed. This turret is preferably made in three parts, the lower ortion or base 110 forming a revolving ta 1e, and having means for rotating same, this means consisting either of the pulley 115 about which is coiled the cable 116, or of a gear adapted to mesh with the pinion shown in Fig. 1, or any other suitable means for rotating the drum 110. A cover plate 111 corresponding to the table 110 forms the other end of the drum, while a tubular shell 112 forms the periphery of of the .drum 110. The drum 110 is journaled on the conically pointed studs 113114 as shown and is provided with suitable notches cooperating with the pawl mechanism 117 whereby the registering positions of the elements such as the prism 60, the lens 70 and the high power lateral sighting system, which will hereinafter be described, may be readily brought to registry and held in that position without danger of accidental movement.

The optical members carried by the drum 110 comprise three systems, namely: the low power system for lateral slghting including the prism and its individual objective 40 (which may be identical with objective 40) the high power system for lateral sighting including the prism 123, the lens combination consisting of members 121 and 122, and an individual objective 40 (which may be identical with objective 40) and the overhead sighting system including the lens 70 and an individual objective 40. These systems are mounted with their vertical axes equidistant from the axis of rotation of the drum 1,10 and are preferably spaced at equal intervals about this axis while the horizontal axes of the two lateral sighting systems extend radially outward.

The head 100 containing the drum 110 is 'mounted at the upper or objective end of the periscope tube as shown in Fig. 3, the window 11 and' the negative lens system 12 which are each held ings, being-arranged co-axial with the lens system inthe periscope tube, and the drum 110 being arranged with its axis of rotation eccentric to and parallel with the axis of the periscope tube lens system in order that by rotating the drum 110, the overhead sighting system, the low power lateral sighting system and the high power lateral sighting system may each be brought into cooperative the numeral 100 indicates in independent mount- 1 relation with its respective window, 10 or 11 and the axis of the lens system in the periscope tube as shown in Figs. 4, 5 and 3 respectively.

Referring now to the optics of the instrument, the system shown in Fig. 6 and in Fig. 7 is the one which is shown incorporated in the instrument shown in Figs. 1 and 2, also in Fi s. 3, 4, and 5, excepting that in Figs. 3, 4, an 5, three systems are provided which may be substituted for one another in the path of light of the instrument, two lateral and one overhead sighting system, and .each system is shown as having itsown individual objective. But since the optical functioning of the two lateral systems of sighting are believed to be not so dissimilar but that with an exposition of the low power system the high power system can readily be understood, the low power system only is included'in the diagram, thus simplifying the diagrams and explanation thereof. For the same reason, the mechanical structure. has been eliminated from these optical diagrams as far as possible, revolving mount has been shown as the means whereby the substituting of the systems was to be effected; moreover, as great a dportion of the system as possible is regarde as stationary.

Referring now more particularly to the optical diagrams, Fig. 6 and Fig. 7 Fig. 6 shows the elements of the system in position for lateral sighting and corresponds to the position which the elements of the instrument are shown to occupy in Figs. 1 and 5 Y and the optical functioning of the apparatus shown in Figs. 1 and 5 may be seen byreference to Fig. 6. Fig. 7 shows the elements of the system in position for overhead sighting, and corresponds to the position occupied by the apparatus shown in Figs. 2 and 4. The functioning of the apparatus shown in Fig. 3 it will be understood, is substantially the same as that of Fig. 5, well shown in Fig. 6, excepting that the lateral view angle will be smaller and the magnification greater. j

, P and P denote light pencils emanating from object O, which pencils are received by the upper or objective prism 60 which is preferably a penta prism as shown, and after being twice reflected, said pencils pass through objective 40 .whereby they are brought to a focus at the focal plane F, at which plane is located diaphragm 42. Continuing on, pencils P and P pass through the reversing system, which comprises lenses 43, 44, 4'5, 46 androof prism 50, whereby the rays of said pencils are again brought to a focus at the plane F, at which plane .is located reticule 51 (shown in the diagram pencils P and P in the usual manner at the exit pupil E. It will be noted that roof prism 50 functions to direct the light pen cils into the said occular, therefore we may refer to said prism as an ocular prism. \Vith the members of the instrument in the position just described (see vFig. 6) any object in the general direction of axis a c 12, and the divergence of tively,

and within the angular limits of the instrument such as indicated by the light pencils P and P may be viewed.

This arrangement of the instrument adapt-s it to use in submarines for viewing vessels in the surrounding waters, it being feasible to rotate the instrument about axis 2) I) as is usual in the case of periscopes of the walk around type. i

For viewing objects in the general direction of axis 2) b, we withdraw or remove prism '60 and utilize negative lens or lens combination 12 as shown in Fig. 7 wherein P and P denote light pencils emanating from object O which pencils after passing through lens 12 are caused to converge at a lesser angle, preferable an angle of convergence corresponding to the angle of convergence of pencils P and P before the latter enter prism 60. After crossing pencils P and P pass through objective 40, are brought to a focus at F pass on through the reversing system, and are again brought to a focus at F where they are picked up by an ocular system as explained in connection with Fig. 6.

In order that the two systems, system for lateral sighting and the system for overhead sighting as shown in Figs. 6 and 7 respectively, may be par-focal, it is necessary that pencils P and P respecwhen received by objective 40, be incident thereon in the same manner that pencils P and P are incident upon said objective. To this end, we place at the crossing point of the principal rays of the pencils P and P a positive lens 70, with its optical center coincident with said crossing point, the said lens being of such power that pencils P and P incident upon the piano surface of objective 40 are made to correspond in every essential particular with the pencils P and P incident upon the same surface of said objective.

' In the present embodiment it is preferred to render parallel the diverging secondary rays of pencils P andP before said pencils are'incident upon objective 40. This is also preferably done Without affecting the direction of the principal rays. Thus if the proper degree of convergence of the principal rays of said pencils is effected by member the secondary rays of said pencils is compensated for by membe 70,'pencils P and P will obviously be incident upon objective 40 in substantially the same manner as pencils P and P are incinamely the dent upon the said objective. Thus, the pencils passing through objective 40, either form the arrangement of elements used in lateral sighting as indicated in- Fig. 6, or from the arrangement of elements used in overhead sighting asindicated in Fi 7, will be brought to a focus at common focal planes. Focal planes F and F, and focal planes F and F? respectiv ly, are common and coincident when the ins rument is constructed to be par-focal.

The turret 110 it will be observed is diagrammatically shown in this figure, the axis ae-x being the axis of rotation thereof. Such portions of the cover 111 and the wall 112 as operate to exclude the extraneous light are also indicated.

Referring now particularly to the optical system shown in Fig. 8: P and 1? indicate light pencils emanating from object 0 the principal rays of said pencils crossing at the optical center of the positive lens 200 whereby the rays of said pencils are brought to a focus at F in the vicinity of the positive lens 201. Said lens 201 causes the principal rays of pencils P and P to converge and cross in substantially the same manner as pencils P and P the secondary rays of pencils Pi and P diverging as shown, which divergence is compensated for by the member in substantially the same manner as explained in the description of the structure shown in Fig. 7. It will be seen that the pencils P and P are incident upon the objective 40 in substantially the same manner as pencils P, P and P P3. The functioning of the system shown in Fig. 8 issubstantially the same as that shown in Fig. 7 excepting that, inasmuch as, in the structure shown in Fig. 8, the twice before reaching objective 40, one less reversion is necessary in the reversing system. Accordingly, in the structure indicated in Fig. 8, penta pri'sm'202 may be used as an ocular prism and a roof prism'203 is preferably used as an objective prism. It will be noted that focal planes P? and P respectively correspond to focal planes F and F In the embodiment of our invention shownin Fig. 8, the me =bers 200, 201 and 7 0 are indicated as being interchangeable with member 203 when it is desired to substitute vision in the general direction of axis 1) b for vision along a lateral axis 0 a. sliding carriage 20 is diagrammatically represented in this case (see Fig.- 8) as the shiftable mount for the elements to be interchanged or substituted. The carriage 20 and the elements carried thereby are indicated in position for lateral sighting in dotted lines and in position for overhead sighting in full lines. The portions of the carriage which operate to exclude the extraneous light are also indicated in this figure.

The

6 tion of Having thus described our invention what we claim and desire to secure by Letters Patent of the United States is:

1. In an optical instrument, the Combinea casing having an eye-piece end and an objective end provided with an opening disposed substant1ally horizontally for ad-. mitting light rays to the eye-piece end and also provided with an openlng disposed sub- 10 stantially vertically, of an ocular and means adjustable into and out of optical cooperation With the vertical" opening to deflect light rays entering therein toward the ocu: lar and to out 01f extraneous light rays entering the horizontal opening.

'2. In an optical instrument, the combination with a tubular casing, an ocular and an objective head-having an opening admitting light rays longitudinally of the casin and also provided with an opening admitting light rays in a direction laterally of the easing, said openings being arranged with intersecting'axes, of means comprising a defleeting optical element and a mounting therefor, said optical element being movable into and out of said axes and adapted when located in operative relation to the last mentioned opening to deflect the light rays entering therein toward said ocular and also serving to intercept the light rays entering the first mentioned opening.

3. In an optical instrument, the combination with a tubular casing, an ocular and an objective head provided with an opening admitting light rays-longitudinally of the casing and another opening admitting light rays in a direction laterally of the casing, of a plurality of optical elements capable of adjustment into and out of optical relationship withsaid openings and a mounting for said elements arranged to cooperate with said openings to close one of them when the other is opened. j

4. In an optical instrument, the combination with a tube, an ocular, and an objective head on the tube having an opening in the, end and an opening in the side thereof, of a mounting ad ustab y supported within the head, a lens system carried by the mounting cooperating with the end opening in the head and means supported on the mounting for deflecting light rays adapted to cooperate with the opening in the side of the head and the ocular.

5. In an optical instrument, the com'bination with a tubular casing, an ocular and an objective head having an opening in the end and an opening in the side thereof, of a mounting adjustable in the head having apertures cooperating with said openings, a

and

lens mounted in one of said openin s h light deflecting means positioned 1n other opening.

6. In an optical instrument, the combination with a casing, an ocular and an objecpos1t1ve lens and tive head having an opening in the end and an opening in the side thereof, of an adjustable mounting in said head having a transverse aperture, permittin the passage of rays of light in a longitudinal direction throu h the head of the instrument, and provic ed with an aperture adapted to register with the opening in the side of said head, a lens located in the first mentioned aperture and a deflector positioned in the second mentioned aperture and means for adjusting said mounting from the exterior of the casing,

7. In an optical instrument, the combination with a system of optical elements comprisingan ocular and an objective, a casing therefor having an open end and provided at one side with an aperture admitting light rays at an angle to the axis of the lens system in the vicinity of'the objective, a deing said aperture to deflect them in the direction of the ocular, a mounting adjustably supporting said deflector whereby it may be moved into and out of operative position, said mounting being arranged to intercept light rays entering the end of the casing when the deflector is in operative position and to cut off light rays entering the aperture in the side of the casing when the deflector is moved into inoperative position.

In an optical instrument, the combination With a casing having an objective head having an opening in the axis of the casing and provided, With a second opening admitting light rays at an angle to said axis, of a mounting within the head carrying a lens and a light deflecting means, said mounting being adjustable to alternately position the lens and deflector in operative relationship to the respective opening in said head. I

In an optical instrument, the combination with a casing having an objective head having an opening in-the axis of the casing and provided with a second opening admitting light rays at an angle to said axis, of a telescope system arranged co-axially Within the casing with its objective disposed in proximity to both openings, an objective prism adapted to be disposed between the objective and the said openings, said prism being mounted to be movable into and out of the axis of the objective and means for moving the prism. a

10. In an optical instrument, the combination with a casing having an objective head having an opening in the axisof the casing and provided with a second openingadmitting light rays at an angle to said axis, of

a telescope system arranged co-axially within the casing with its ob ective disposed in proximity to both openings, one or more negative lenses, mounted co-axial with and in proximity to the first named opening, a

' an objective prism mounthead having a light of-the objective and cooperating respectively with the first named opening and the objective and with the last named opening and the objective, a movable mounting for the positive lens and objective prism, and means for operatively moving the mounting.

11. In a periscope, the combination of a periscope tube and an ocular, an objective head having an opening admitting light rays longitudinally of the tube and a second opening admitting light rays laterally thereof, a plurality of optical systems adapted to cooperate with said openings and the ocular, an adjustable mounting for the optical systems, and means for moving the mounting including a shaft extending along the inside of the periscope tube, having an operating portion adjacent the ocular.

12. In a periscope, the combination of a periscope tube and an ocular, an objective head having an opening admitting light rays longitudinally of the tube and a second opening admitting light rays laterally thereof, a plurality of optical systems adapted to cooperate with the said openings and the periscope tube, a tubular adjustable mounting movable in the direction of its longitudinal axis, a sleeve in which the mounting is slidably held, an aperture in the sleeve registering with each of said light admitting openings and an aperture registering with the periscope tube, a plurality of pairing apertures in the mounting adapted to cooperate selectivelywith the apertures in the sleeve whereby the mounting may open a selected light path while excluding light from all other sources, one of the optical systems being mounted in registry with each pair of apertures in the mounting, means for shifting the mounting, and means for securing the mounting against accidental movement.

13. In a periscope, the combination of a periscope tube and an ocular, an objective admitting opening substantially coaxial with the longitudinal axis of the tube and a lateral light admitting opening arranged with its axis angularly disposed with relation to the said axis of the tube, amounting rotatable about an axis substantially parallel to the axis of said tube, a plurality of optical systems each individual to one or the other of said light admitting openings and adapted to be carried wholly or in part by said mounting, means for moving said mounting rotatably about its axis whereby each of said optical systems may be selectivelybrought into operative relation with the periscope tube and that light admitting opening with which the individual system is desi ed to cooperate.

14. An optical system for periscopes having a pair of light admitting apertures, said system comprising, a telescope system adapted to be wholly or in part common to .both

. arrangement apertures and coaxial with one of them, an 7 optical prism individual to one aperture, a lens system including one or more negative lenses individual to the other aperture, said prism and lens system adjustably cooperating with their respective apertures and the telescope system, and means for excluding light from one aperture when light rays are admitted through the other.

16. An optical system for a periscope having a pair of light admitting apertures, said system comprising, a telescope system adapted to be wholly or in part common to both apertures and. coaxial with one of them, an optical prism individual to one aperture, a system of positive lenses individual to the other aperture, said prism and lens system adjustably-cooperating with their respective apertures and the telescope system, and.v

means for excluding light from one aperture when light rays are admitted through the other.

17. An optical system for a periscope having an aperture for admitting lateral light rays and an aperture for admitting longitudinal light rays, said system comprising, a telescope system adapted to be wholly or in part common to both apertures and co-= axial with the latter, a prism adapted to defiect the lateral light rays along the axis of the telescope system, a lens system adapted to retract the longitudinal light rays to amplify the angle of view of the telescope system in a longitudinal direction, said prism and lens system each being adapted to cooperate with the telescope system to the exclusion of the other.

18. An optical system for periscopes having a pair of light admitting apertures, said system comprislng, a telescope system adaptedto be wholly or in part common to both apertures, a supplementary optical system individual to each of said apertures, each of said supplementary optical systems being adapted, in turn, to selectively cooperate with their respective apertures and the telescope system, and means for rendering the of the telescope system with each of the supplementary systems parfocal.-

19. An optical system for a periscope hav- --ing a pair of light admitting apertures, said optical system comprising, a telescope systance between the objective and the lens betem adapted to be wholly or in part common ing such that the pencils of light passing to both apertures, one or more interchangefrom said lens to the objective will cross at able supplementary optical systems india point therebetween, and a lens positioned vidual to each of the said light admitting at the crossing point of said light pencils apertures, said supplementary optical sysand adapted to deflect the secondary rays of tems each being adapted to cooperate with said pencils without deflecting the principal its respective light admitting aperture and rays thereof.

the telescope system, a positive lens arranged 21. In a sighting apparatus, the combinabetween one or more of the supplementary tion. of a lens tube, and an image-forming optical systems and the telescope system and optical system comprising a side lens, a sky functioningat the crossing point of the prinlens, the axes of said lenses intersecting, and cipal rays of light adapted to pass from said an objective reflecting surface having one supplementary optical systems to "the teleposition at said intersection, and another p0- scope system whereby to render each arsition out of line with the axis of said sky rangement of the telescope with the various lens.

supplementary optical systems par-focal, and 1 means for excluding extraneous light. 20. In an optical instrument. the combination with an objective, of a view angle modi- \Vitnesses:

fying lens adapted to cooperate with the ob- WILLIAM G. \Voonwonnr,

JECtHG in spaced relation thereto, the dis- GEORGE A. PAGE. 

